Samuel Bowles writes:
At the close of the eighteenth century ... Haiti was probably the richest society in the world.
Is the above claim true?
It has certainly been argued in various places that Haiti was the "richest" colony. It's obviously difficult to reconstruct modern measures of wealth such as per capita income for historical territories, and the metric of "rich" that mattered in the day was how much revenue could be extracted by the colonial government, so assessments may be skewed towards this. My books are boxed at the moment, but this is what I could find based on the footnotes from Understanding Power (ch 10 p62).
Citing Hans Schmidt, The United States Occupation of Haiti, 1915-1934, New Brunswick, NJ: Rutgers University Press, 1971, pp. 19-20:
At the time of the French Revolution, Saint Domingue [Haiti] was the wealthiest European colonial possession in the Americas. As early as 1742 the sugar production of Saint Domingue exceeded that of all the British West Indies, and on the eve of the revolution the colony accounted for more than one-third of the foreign commerce of France. In 1789 French trade with Saint Domingue amounted to £11 million, while the whole of England's colonial trade totaled only £5 million. In the same year the ports of Saint Domingue received 1,587 ships, a greater number than Marseilles, and France employed 750 ships exclusively for the Saint Domingue trade. The chief exports of the colony were sugar, coffee, cotton, indigo, molasses, and dyewoods. The French built an elaborate network of roads, irrigation systems, and magnificent plantations.
Citing Paul Farmer, The Uses of Haiti, Monroe, ME: Common Courage, 1994, p. 63:
At one time or another, the colony was first in world production of coffee, rum, cotton, and indigo. On the eve of the American Revolution, Saint-Domingue [Haiti] -- roughly the size of the modern state of Maryland -- generated more revenue than all thirteen North American colonies combined. By 1789, the colony supplied three-fourths of the world's sugar. Saint Domingue was, in fact, the world's richest colony and the busiest trade center in the New World.
And citing Patrick Bellegarde-Smith, Haiti: the Breached Citadel, Boulder, CO: Westview, 1990, pp. xviii:
In the second half of the eighteenth century... [Haiti] created more wealth than any other colony in the world. At that time, 50 percent of France's transatlantic commerce involved Haiti, and nearly 20 percent of the French population depended on trade with Haiti for its livelihood... Overall investments in the Haitian economic infrastructure were meager compared to the enormous profits and trade advantage gained by France. Economically, Saint-Domingue [Haiti] was the world's most profitable colony. It soon became known as "the pearl of the Antilles" and was the standard by which the profitability of other colonies was judged.